NEW YORK (Reuters Health) - A complete response on CT scan is not conclusive in assessing the presence of metastases after chemotherapy for colorectal liver metastases, French researchers report in the August 20th issue of the Journal of Clinical Oncology.

Dr. Stephane Benoist and colleagues at the Hopital Ambroise Pare in Boulogne studied 38 patients treated for colorectal liver metastases in their institution. Eligibility for the study included fewer than 10 liver metastases before chemotherapy, disappearance of one or several spots on CT scan and ultrasound after chemotherapy, surgery with intra-operative ultrasound within four weeks, no hepatic disease and follow-up at least one year after surgery.

There were a total of 183 liver metastases before chemotherapy and 66 disappeared afterward as assessed by CT scan. Dr. Benoist and colleagues found persistent macroscopic disease at the site of surgery in 20 of the 66 liver metastases.

Of 31 liver metastases considered completely cured after surgery by intraoperative imaging, 23 had recurred in situ.

Overall, there was persistent macroscopic or microscopic residual disease or early recurrence in 55 of the 66 index liver metastases, or 83%.

Dr. Benoist notes that there was macroscopic evidence of disease on exploratory surgery in more than 25% of cases and microscopic disease was found in 80% of patients with no obvious disease.

"The major question for the surgeon is whether the site of metastases that have disappeared should be included in the resection or be left in place," the authors write. "This study demonstrated that microscopic cancer persists in most of these sites...Thus, in most cases, resection of the of the sites of initial metastases is necessary."